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NIHR Signal Routine use of a mechanical compression device is no better than manual chest compression in cardiac arrest

Compared with manual compression, mechanical chest compression does not improve survival rates after cardiac arrest. However, in situations where manual compression may be difficult, such as in a moving ambulance, mechanical compression may still be an option.

Each minute that a person waits for treatment after a cardiac arrest can make a difference of up to 10% to their chance of survival. Cardiopulmonary resuscitation (CPR) is the crucial first step to keep oxygen circulating to vital organs such as the heart and brain.

While in theory, the use of automated chest compression could ensure optimum CPR delivery, this is not supported convincingly by the evidence. This review shows little difference between the two methods regarding survival without brain damage. As such, cost and practical considerations mean that automated devices may be best reserved for situations where manual CPR performance would be compromised.

Cardiovascular system disorders, Emergency and urgent care, Acute and general medicine

Why was this study needed?

Each year around 60,000 people in the UK suffer a cardiac arrest at home or in public places. Of these, fewer than 10% who receive a resuscitation attempt will survive.

After a cardiac arrest prompt action is crucial to keep oxygen circulating around the body until a defibrillator can be used. Full CPR involves both chest compressions and rescue breaths. CPR is physically demanding, and the person performing it is likely to tire. Consistency is one of the supposed benefits of mechanical CPR, but this is offset by cost and difficulty in deployment.

The previous Cochrane update of this review in 2014 concluded that the existing research was not of sufficiently high quality to draw any conclusions. This update sought whether research published since would make a difference.

What did this study do?

This Cochrane systematic review included 11 trials comparing manual CPR with that provided by mechanical devices for 12,944 people with out-of-hospital or in-hospital cardiac arrest. All resuscitation attempts were by trained healthcare professionals.

Of five new trials in this update, three were large scale randomised controlled trials contributing 90% of the 12,944 included participants. The majority of trials focused on out of hospital cardiac arrests. One was conducted in the UK, and another was a multinational trial including the UK.

The quality of CPR was not reported in nine studies. As the authors state, the quality of manual CPR is particularly important. Poor manual CPR could give an unreliable benchmark. Also, the authors note that deployment of automated devices is prone to cause breaks in compressions or delays to defibrillation. No meta‐analysis was possible due to the wide variation between study characteristics (heterogeneity).

What did it find?

Two studies had similar rates of survival to hospital discharge with a good neurological outcome between the mechanical and manual groups (8.3% vs 7.8% for one and 4.1% vs 5.3% for the other).

One older study demonstrated a reduced rate of survival to hospital discharge with a good neurological outcome for mechanical CPR (3.1% vs 7.5%; risk ratio [RR] 0.41, 95% confidence interval [CI] 0.21 to 0.79). Good neurological function was defined as equivalent to 1 or 2 on the Cerebral Performance Category scale, with a range of 1 (intact function) to 5 (brain death).

None of the four studies addressing survival to hospital admission reported a difference between mechanical and manual CPR, with rates around 20% to 28% in the larger trials (7,224 patients overall).

For survival to hospital discharge, over half of the seven studies showed no difference between the two methods (8,067 patients overall).

No studies demonstrated a difference in adverse events or injuries between the two groups, but data quality was low.

What does current guidance say on this issue?

Resuscitation Council 2015 guidance recommends that automated devices should only be used in circumstances where high-quality manual chest compressions are difficult or potentially dangerous.

Making sure chest compressions, regardless of the method used to deliver them, have the appropriate depth and rate is crucial. It also highlights the potential for interruption to CPR during the deployment of mechanical devices and stresses the need for adequate staff training to minimise this risk.

What are the implications?

In principle, using automated devices to deliver CPR could be a way to provide sustainable, high-quality compressions compared with humans who tire. However, the evidence so far does not show superior performance over manual compressions.

Difficulties in the deployment of automated devices may lead to breaks in compressions or delay in defibrillation. With adjustments to protocols and staff training, it might be possible to define a situation where automated devices are useful and as good as manual compressions.

Expert commentary

High-quality chest compressions are important treatment for cardiac arrest, but they are physically demanding and difficult to sustain. Mechanical CPR devices are conceptually attractive as they automate the process of delivering chest compressions and do not fatigue with time. However, devices are expensive and can be difficult to deploy, leading to harmful interruptions in chest compressions.

This review did not find evidence that mechanical CPR devices improved survival in out of hospital cardiac arrest. Consistent with the position of the Resuscitation Council (UK), the authors advise that mechanical chest compression devices are a reasonable alternative to high-quality manual chest compressions in situations where sustained high-quality manual chest compressions are impractical or compromise provider safety.

If mechanical devices are used, it is critical that teams are highly trained, that interruptions to CPR are minimised during device deployment, and that team performance is evaluated regularly.

The commentator declares being the principal investigator of a trial included in this review

Expert commentary

The quality of chest compressions – rate, depth, and avoiding interruptions – is an important component of CPR. Humans get tired very quickly when delivering manual CPR, so mechanical CPR devices were introduced by some ambulance services worldwide in recent years, despite uncertainty about their effectiveness.

Several large randomised trials have now been published, and this updated Cochrane review concludes that mechanical CPR has not been shown to be better than manual CPR in routine use. International guidelines suggest there may still be a role for mechanical CPR in specific circumstances such as if a patient requires ongoing CPR during transport to hospital for emergency coronary intervention, or other specialist treatment.

But the greatest lifesaving potential rests with the community – calling for help, starting CPR and using a defibrillator if available.

Professor Tom Quinn, Associate Dean for Research and Innovation and Director for the Centre for Health and Social Care Research, St George's University London

The commentator declares co-authorship of trials included in this review